Boiler control system



Aug. 14, 1962 L. J. KMIECIK ETAL BOILER CONTROL SYSTEM Filed Aug. 7,1959 mare/v,

ite

Patented Aug. 14, 1962 3,049,145 BOILER CGNTROL SYSTEM Leopold J.Kmiecik and Leo W. Kaczmarek, Chicago, Ill., assignors to McDonnell &Miller, Inc., Chicago, Ill., a corporation of Delaware Filed Aug. 7,1959, Ser. No. 832,184 3 Claims. (Cl. 137-414) Our present inventionrelates to control systems for boilers, and more particularly to acontrol system for maintaining the water level in a boiler at asubstantially constant predetermined level.

Steam is used in rnany commercial processes in the treatment ofmaterials and otherwise, and in most instances it is desirable that thesteam be utilized at a constant predetermined pressure to besatisfactory. A boiler is usually employed to afford a steam source andas the steam is exhausted from the boiler the liquid within it isconsumed and must be replenished. In conventional systems presently inuse, the liquid level is usually sensed by a oat, and after the floathas dropped a predetermined amount, liquid is fed to the boiler until adesired level is reached. In present systems before supply liquid is fedto the boiler, the liquid level must drop appreciably and to an extentcausing undue lowering of the pressure within the boiler for appropriateuse in certain processes of the steam generated in the boiler. Thus,when the liquid in the boiler has diminished so that it is at a level atwhich supply liquid is fed to the boiler, the pressure within the boilerand the discharge pressure of the steam from the boiler may be below thedesired pressure for the process in which the steam is being used, orthe level of the liquid in the boiler at which feeding of the supplyliquid is terminated may be such that the pressure within the boiler isin excess of that desired or required.

lt is an object of our invention to avoid the aforementionedshortcomings by providing a control system for a steam boiler in which,when steam is discharged from the boiler, supply liquid is delivered tothe boiler at a rate to maintain liquid in the boiler substantially at aconstant predetermined level.

ln order to achieve the aforementioned object, we provide a controlsystem for a boiler affording a source of steam comprising, levelsensing means associated with the boiler, means affording a continuouscirculating source of supply liquid for the boiler, and flow controlvalve means between the supply liquid and the boiler caused to beactuated by the level sensing means to afford upon discharge of steamfrom the boiler for the feeding of supply liquid to the boiler at a rateto maintain the liquid in the boiler at a substantially constantpredetermined level.

A further object of our invention is to provide a control system asabove related in which the level sensing means has connection with asource of fluid under pressure and includes a oat responsive to theliquid level in the boiler, and in which movement of the float effectscontrol of the application of the source of fluid under pressure to theaforementioned ow control valve means so that the latter controls theflow of liquid from a liquid supply source to the boiler to maintain thelevel of the liquid in the latter at a substantially constantpredetermined level.

A further object is to provide acontrol system as last described inlwhich means including a pump, is provided to maintain liquid of theliquid supply source for the boiler in continuous movement for deliveryto the boiler without starting and stopping of such supply liquid.

A further object of our invention is to provide a system as noted in-which a common liquid source serves as the aforementioned source of uidunder pressure associated with the level sensing means and flow controlvalve means, and for replenishing the liquid supply source for theboiler.

A further object of our invention is to provide a system asaforementioned in which the liquid supply source for the boiler isretained in a receiving tank which in turn has connection with thecommon liquid supply, and with conventional feeder means being providedfor regulating the flow of liquid into the receiving tank.

The above and other objects and advantages of our invention will appearfrom the following detailed description of a preferred embodiment of ourinvention.

Now in order to acquaint those skilled in the art with the manner ofconstructing and utilizing a control system in accordance with theprinciples of our invention, we shall describe in connection with theaccompanying drawing a preferred embodiment of our invention.

The single lFIGURE. of the drawing is a largely diagrammatic view of acontrol system for maintaining a predetermined substantially constantliquid level. in a boiler.

In the drawing the control system of our invention is shown largelydiagrammatically for purposes of simplicity and in View of the fact thatthe several components of the system .may comprise any of many well andlong known devices and appurtenances of the art.

A steam generator, which may take the form of a boiler for providing asource of steam is indicated at 1 in the drawing. The boiler may be ofany conventional and desired construction, fired in any known manner,for converting a body of liquid to vapor, such as water to steam, whichis drawn off in any suitable manner as indicated through an outletconduit `3. A source of water under pressure for replenishing the boiler1 is afforded by a pipe line 4 from which a branch pipe 5 extends to theinlet of a known water feeder device 6. A pipe 7 extends from the outletof feeder 6 to a liquid or water supply source, such as a conventionalreceiving tank 8. The feeder v6, as shown, is connected by conduits 9and 10 to the top and bottom, respectively, of the receiving tank 8, andprovides a -water level in the float chamber 12 of the feeder 6corresponding to the water level of the receiving tank. A pivoted oat 13for feeder 6 controls connecting and disconnecting of the inlet andoutlet of the feeder 6 to provide for the admission of water toreceiving tank 8 as dictated by position of the float 13 all as is wellknown. Outlet means for the receiving tank comprises an outlet pipe 14extending from the bottom of receiving tank 8 to the inlet of a one waycheck valve 15, a pipe 16 which extends from the outlet of check valve15 to the inlet of a known form of centrifugal pump 17, and a pipe 13which extends from the outlet of the centrifugal pump 17 to the inlet ofa flow control valve 19. A .pipe or boiler feed line 20 extends from theoutlet of flow control valve 19 to the water chamber of the boiler 1. Itwill be observed that bypass piping 23 including a pressure relief valve24 is connected at one end in advance of the inlet of centrifugal pump17 and at the other end beyond the outlet of the pump. The pump 17, whenthe system is in operation is continuously driven and when valve 19 isin open position, water from the liquid supply source or receiving tank8 flows through pipe 14, the one-way check valve 15, pipe 16, into theinlet of the pump 17, out the outlet of the pump through pipe 18,control valve 19, and pipe or boiler feed line 20 into the boiler. Whenthe control valve 19 is closed and it being remembered that the pump 17is continuously in operation, the pressure relief valve 24 opens andwater in the supply line for the boiler circulates from the outlet ofthe pump 17 through bypass piping 23 including valve 24 and back intothe inlet of the pump and continues in that fashion until valve 19 isopened -whereupon pressure relief valve 24 closes.

The control system of our invention further includes a level sensingdevice or means indicated generally at 39 and which device is of knownconventional construction. It in its broad aspects comprises a oatchamber 32 within which a `iioat 33 is disposed with the oat chamberbeing connected by pipes 34 and 35, respectively, to upper and lowerportions of the water compartment of boiler 1. The oat 33 is movable inresponse to the liquid level in the boiler 1. The oat 33 has connectionthrough suitable'linkage 38 with a valve 39 for disposing the latter inopen and closed positions with respect to valve seat 40; The previouslymentioned source of liquid under pressure at pipe 4, has connection bymeans of pipe 42 to pressure reducing valve 43, and by pipe 44 to abalancing valve 46 from which pipe 47 extends to the inlet of a valvehousing 41 at the lower end of the level sensing device 30 and abovevalve seat 4i). The outlet of the valve housing of the level sensingdevice below valve seat 40 is connected by pipe 50 to the receiving tank8. As shown, the valve housing 41 is in fluid sealed relation withrespect to float chamber 32 of the level sensing device as afforded bythe partition 60 and bellows 61 extending between valve 39 and partition60. The pipes 47 and 50 may be considered `as constituting a supply linethrough which fiow of liquid under pressure is under the control of thevalve means afforded by valve 39 and its seat 40. As shown, a vent 53 isprovided for venting the receiving tank 8. It will be observed also thata pipe or uid pressure line 55 ahead of the inlet of the level sensingdevice extends from conduit 47 to the flow control valve 19. In theparticular embodiment of our invention herein shown and described, theyiiow control valve means 19 includes servo operating means in the formof a diaphragm S7, and a valve member '58 cooperating with a valve seat59 between the inlet and outlet of the valve for opening and closing thesame.

In the control system above described, as steam is withdrawn from boiler1 through the steam take-oi means 3, the water is, of counse, consumedand the iloat 33 of the level sensing device 30 responds to change inthe aforementioned liquid level, which is effective to dispose the valve39 in open position with respect to valve seat 40. When the liquid levelin boiler 1 is at the desired predetermined level affording the desiredpressure condition in the boiler, the valve 39 is seated on valve seat40, and the full pressure of the source of liquid under pressure in thesupply pipe is imposed on diaphragm 57 of valve -19 seating valve S onseat 59 and no Water from the receiving tank 8 is admitted to theboiler 1. Upon lowering movement of float 33 `of the float sensingdevice 30 causing valve seat 39 to assume an open position relative tovalve seat 40, liquid flow is established from the inlet to the outletof the valve means of the level sensing device, which movement of liquidelects reduction in pressure in pipe or uid pressure line 55 acting onthe diaphragm 57 of the diaphragm valve thus moving valve 58 oit ofvalve seat 59 so that water is admitted through pipe or boiler feed lineinto the boiler. As before lmentioned in the closed position of valve 5Son valve seat 59, water from 4 the outlet of centrifugal pump 17 passesthrough the pressure relief valve 24 and into the inlet of the pump sothat a portion of the supply water for the boiler is always in motion.Thus, immediately upon opening of the diaphragm valve, a moving sourceof supply water is immed iately fed into the boiler 1.

In the operation of the control system of our invention the movement ofthe lioat 33 of the valve means of the level sensing device 30 respondsto minor change of liquid level in the boiler, and, in fact, the valve39 has a substantially continuous modulating eect with respect to itsvalve seat 4l). Thus, minor changes of pressure are applied to diaphragm57 of the llow control valve 19 to dispose valve 58 to open and closedpositions with respect to seat 59, affording the substantiallycontinuous replenishment of water to the boiler in an amount equal tothe steam being withdrawn from the boiler so as to maintain the level ofthe ywater in the boiler at a substantially constant predeterminedlevel.

In the preferred form of our invention the water under pressure at pipe4 serves to feed the receiving tank 8 and also serves to provide apressure source of fluid pressureV acting through the valve means of thelevel sensing device 30 for actuating valve 19. However, it will beclear that another and different form of iluid pressure source mayl beresorted to for the aspect last noted although for purposes of economythe common source disclosed is preferred.

While We have shown and described what We consider to be a preferredembodiment of our invention, it will be apparent that revisions andmodications may be readily made therein without departing from thespirit and scope of our invention.

We claim:

l. A control system for a boiler comprising level sensing meansincluding a iloat chamber having fluid connection with the boiler; ailoat in said float chamber movable in response to the liquid level inthe boiler; a supply line having connection with a source of liquidunder pressure; valve means including a valve housing connected in saidsupply line and in iluid lsealed relation with respect to said floatchamber; said valve means including a valve seat and a cooperating valvemember movable relativeto said valve seat for modulating the rate ofliquid ow therethrough in accordance with movement of said valve membertoward and away from said valve seat; pressure operated control valvemeans having an inlet, an outlet, and servo operating means between saidinlet and said outlet for controlling ilow of liquid under pressuretherethrough; a boiler feed line extending between the outlet of saidcontrol valve means and said boiler for conducting liquid to saidboiler; a fluid pressure line connecting said supply line with saidservo operating means of said control valve means; a receiving tankhaving an inlet and an outlet; said supply line down stream of saidvalve in said supply line having connection with the inlet of saidreceiving tank; outlet means for said receiving tank connecting theoutlet of the same with the inlet of said control valve means; and meansconnecting said float with said valve member providing for conjointmovement of said valve member with said iloat so that as said valvemember moves away from said valve seat upon lowering of the liquid levelin the boiler, the pressure in said supply line is reduced, and as saidvalve member moves toward saidV 2. The control system of claim lcharacterized by the provision of bypass means associated with saidoutlet References Cited in the lile of this patent UNITED STATES PATENTSConnet Mar. 14, 1911 Williams May 30, 1911 Osbourn Nov. 17, 1914Rodenacker Sept. 11, 1956 Thomas Apr. 30, 1957 Topol Ian. 27, 1959

